Insert assets with title instead of id

[saturnflyer]

Every time I insert an asset I use the title. The titles rarely change if ever and the id is completely arbitrary and unhelpful information.

Instead of inserting

<r:assets:image id="123" />

it should be

<r:assets:image title="my-awesome-image" />

hmm. i think i prefer it being something that is not user editable; perhaps filename. what happens when you have two assets with the same filename and/or title?

[saturnflyer]

My motivation is that it uses something that makes sense to the user. The ID is of absolutely no value when you want to know what image it is.

If it uses filename, that's fine, as long as I understand it AND as long as we actually show that filename somewhere

[SamWhited]

Right now the filename isn't unique and find_by_asset_file_name will return the first one. While it would be easy enough to validate the uniqueness of the filename, the user can still change it by uploading a new file so it kind of defeats the point.

EDIT: See commits below for example. Right now it is extremely confusing if there are multiple files with the same name.

EDIT 2: Committed the cardinal sin of Git and force overwrote some history. The third commit has everything (first two aren't in the tree anymore).